Ukrainian counterintelligence investigators said Tuesday that they thwarted a plan by Russian agents to assassinate President Volodymyr Zelenskyy and other high-level officials. Two colonels in the State Guard of Ukraine, which protects top officials, were arrested on suspicion of treason for enacting the plan, Ukraine's state security service said in a prepared statement, which added that the plot was drawn up by Russia's Federal Security Service. Moscow did not immediately comment on...